The White Horse by Cynthia D. Grant

The white horse is what Raina calls her mother’s drug habit–first a small, pretty pony that makes you happy, but later on, a huge ravenging stallion that demands attention at any cost. Because of her mother’s addiction, Raina usually stays away from home and instead runs the streets with her boyfriend Sonny, who’s also a junkie. When she discovers she’s preganant, the only person she can turn to is her sympathetic teacher, Ms. Johnson. Can Raina rein in her own white horse? Or will she get taken for a ride?